Lighting systems play an important role in the experience of the cabin space on aircraft systems. They ensure passenger comfort, enable communication with the crew and enhance security. Aircraft manufactures and airliners have identified this as a means of gaining competitive advantage, e.g., through improving the passenger experience with new lighting features to improve the individual passenger's comfort or by creating the desired moods and ambience in shared cabin spaces. Some of these features are already being developed for new aircrafts like the A380 and the 7E7, more are proposed for aircrafts still in conception.
To achieve the full benefit from these lighting systems, the degradation of the individual lighting components (LEDs) should be monitored closely, as subtle changes in the luminescence of different components may distort the effects being aimed at by the lighting system. Aside from monitoring individual lighting components, the continuous monitoring of other components in the unit is important in order to preemptively identify faults or health states that impact the lighting system as a whole and to correct this in a preventive maintenance process.
A conventional approach in monitoring the degradation of lighting systems is based on using data from endurance tests of sample LEDs carried out after production and used to predict the useful economic life of the LEDs. This process may involve randomly selecting LEDs from the production run and exposing them to a series of tests in a specially constructed measuring station. Testing conditions may include the following variables: current flow, power output, ambient temperature and stress on the LEDs. By programming the conditions in the measuring station with extreme values of the controlling variables (e.g. using very high or very low temperature values), the aging process of the devices may be accelerated, this way data for the rate of degradation of the LED's are collected and used to predict the theoretical life span of the devices. This data are then used to develop a policy for the maintenance of the devices and their replacement, when required, at strictly defined times in a scheduled maintenance process. Monitoring of other non-lighting components (e.g. the illumination ballast unit, or IBU), may be separately performed and collected, each component being graded as to its individual health state, faulty, normal etc.
The conventional method is characterized by the following: For example, the endurance tests on the lighting elements to derive life-cycle estimation data carried out in a simulated environment to accelerate the aging process on the devices may not reflect the operating environment of the lighting systems in the aircraft cabin. Hence, the obtained data which is the basis of the monitoring and maintenance process may not match the run time experience of the LEDs and of the lighting systems containing them. This may lead to inaccuracies in predicting mean-time-to-failure (MTTF) estimates of components and the lighting system, resulting in greater complexity (in time, intractability, etc) and costs of the maintenance process.
A further feature of the aforementioned convention approach may be that the maintenance logic and accelerate test data used for this purpose are fixed at build time and there is no provision made to learn from the experience of operating the system to improve its monitoring and maintenance. Data and information collected during the current operating life of the system may not be used to provide a more accurate prediction of the components' or system's health state or MTTF.